CMAKE: Make CMake config idempotent w.r.t. target discovery and creation

[vyasr]

What

This PR makes it safe to call find_package(ucx) multiple times in the same scope in CMake.

Resolves #9614

Why ?

In complex build environments where multiple packages may depend on ucx, it may be found twice in different parts of the CMake code. Depending on the relative scope of these find_package calls, calling find_package(ucx) multiple times in the same or nested scopes is a common occurrence.

How ?

This PR changes the ucx-targets.cmake file to check which targets are defined before trying to create new ones. It exits early if all the desired targets have already been created in this scope.

[pentschev]

@vyasr could you squash commits? I think in general only one commit per PR is expected, the first one seems to be named correctly but the latest isn't, squashing them into a single commit should resolve that and be in line with what is normally expected in this repo.

[vyasr]

@vyasr could you squash commits? I think in general only one commit per PR is expected, the first one seems to be named correctly but the latest isn't, squashing them into a single commit should resolve that and be in line with what is normally expected in this repo.

Done.

[vyasr]

I don't think the one failure is related, but I don't know ucx well enough to be sure. It seems like an unrelated build issue on the runner though.

[pentschev]

I don't think the one failure is related, but I don't know ucx well enough to be sure. It seems like an unrelated build issue on the runner though.

I agree, the failure is here and seems to be related to mlx5/verbs:

Check for ./uct_info_static
tcp... ok
self... ok
sysv... ok
posix... ok
dc_mlx5... fail
rc_mlx5... fail
ud_mlx5... fail
rc_verbs... fail
ud_verbs... fail
cma... ok
failed to check tl in ./uct_info_static
##[error]Bash exited with code '1'.

@yosefe @brminich could you please confirm the above isn't related? I think this is ready for review too, could you please take a look when you have the chance?

[tvegas1]

merged as #9696